A novel adaptive droop control strategy for SoC balance in PV-based DC microgrids

• Published in: ISA transactions Vol. 141; pp. 351 - 364
• Main Authors: Li, Boxi, Yu, Chang, Lu, Xiaoqing, Wang, Fanrong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2023
• Subjects: Battery energy storage system; DC microgrid; Sliding mode controller; SoC balance; Stability; Battery energy storage system; Stability; DC microgrid; SoC balance; Sliding mode controller
• ISSN: 0019-0578; 1879-2022
• DOI: 10.1016/j.isatra.2023.07.008

Battery energy storage systems (BESSs) are generally used as a buffer stage for photovoltaic (PV) power generation to tolerate the output power unpredictability in DC microgrids, in which the State-of-Charge (SoC) balance is a necessary and urgent issue to be solved. To this end, an integral feedforward sliding mode controller (SMC) is adopted to replace the traditionally proportional integral (PI) controller such that the voltage response speed of the converter in each BESS can be significantly enhanced. Further, a novel adaptive droop control strategy for SoC balance with three different working modes is proposed, in which all batteries can be cooperated through three different stages corresponding to their different SoC degrees. Compared with most existing SoC balancing approaches, the proposed SoC strategy can improve the transient performance for the BESSs and their robustness against the volatility of PV output powers. The effectiveness of the proposed SoC balancing strategy is verified through a simulation in a DC microgrid network consisting of several PV generators, batteries, and loads utilizing Simulink/SimPower Systems. •The proposed adaptive droop control strategy can adjust all converters' switching frequencies initially as the reference voltage changes, which can improve the robustness of the BESSs against the unpredictable power fluctuations of PVs.•The proposed novel SoC balancing strategy is designed with three different operation modes, aiming to reducing/accelerating the charging/discharging speed as batteries are in overcharge/undercharge states.•Both the system transient performance and the battery operation safety can be significantly improved.